What Is The Surge Arrester Voltage Equalizing Ring? Why Does High Voltage Level Need To Be Installed?
A corona ring—often called a grading ring—is a circular conductive device mounted on electrical apparatus. Its primary role is to distribute the electric field gradient evenly around the equipment, preventing localized electrical stress that leads to corona discharge and insulation breakdown.
How Corona Rings Protect High-Voltage Assets
At elevated voltages, the electrical stress near the top terminals of a lightning arrester becomes extremely high. This uneven distribution can prematurely damage the internal varistors, leading to catastrophic equipment failure during overvoltage events.
To solve this, the grading ring physically alters the electric field lines. It ensures the topmost varistor units do not carry a disproportionate amount of the voltage stress, thereby preserving system integrity.
Voltage Thresholds: When Are Grading Rings Necessary?
While a compact 12kv surge arrester operates safely without extra shielding, transmission-level equipment requires active stress control. System designers typically introduce grading rings once system voltages surpass 72.5 kV to guarantee long-term grid reliability.
| Equipment Type | Voltage Class | Corona Ring Requirement |
| Distribution Protection Unit | 10 kV - 36 kV | Not required for standard installations |
| Substation Overvoltage Shield | 72.5 kV - 110 kV | Optional based on environment |
| Transmission Voltage Guardian | 132 kV and above | Mandatory to prevent breakdown |
Selecting the Right Protection for Substation Safety
Choosing the correct shielding configuration depends heavily on the specific grid application and environmental pollution levels:
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For standard distribution grids, a compact 132kv lightning arrester utilizes tailored rings to prevent radio interference in damp conditions.
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In heavy industrial zones, installing a robust 132kv surge arrester with a dual-ring setup mitigates the risk of flashovers caused by airborne contaminants.
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For ultra-high voltage substations, specialized large-diameter rings are deployed to shield the sensitive active elements of a 132 kv lightning arrester from continuous power-frequency stress.
